U.S. patent No. 4,105,776, issued Aug. 8, 1978, describes a group of thioalkanoyl derivatives of azetidine-, pyrrolidine- and piperidinecarboxylic acid compounds having the structural formula ##STR7## wherein the symbols can be, inter alia, as follows: R.sub.g can be hydrogen, lower alkyl, phenyl, substituted phenyl, phenyl-lower alkyl, ##STR8## R.sub.h can be hydrogen, R.sub.i can be hydrogen or lower alkyl, R.sub.j can be hydrogen, hydroxy or lower alkyl, R.sub.k can be hydroxy, --NH.sub.2 or lower alkoxy, n can be 0, 1 or 2 and m can be 1, 2 or 3.
U.S. Pat. No. 4,129,566, issued Dec. 12, 1978, describes derivatives of dehydrocyclicimino acids having the structural formula ##STR9## wherein the symbols can be, inter alia, as follows: R.sub.i, R.sub.l and R.sub.m can each be hydrogen or lower alkyl and n' can be 0 or 1.
Belgian Pat. No. 861,454, published June 2, 1978, describes compounds having the structural formula ##STR10## wherein the symbols can be, inter alia as follows: R.sub.n can be hydrogen, lower alkanoyl or benzoyl, R.sub.o, R.sub.p and R.sub.q can each be hydrogen or lower alkyl, R.sub.r can be hydroxy or lower alkoxy, m' can be 1, 2 or 3, n" can be 0, 1 or 2 and M'+n" can be 2 or 3, p can be 0 or 1 and X can be O, S, SO or SO.sub.2, m' being 2 and n" being 1 when X is O.
The compounds set forth above are useful as inhibitors of the conversion of the decapeptide angiotensin I to angiotensin II, and are, therefore, useful in reducing or relieving angiotensin related hypertension.